Standard procedures for preparing tissue samples for microscopic examination involve embedding the tissue sample in paraffin and slicing the paraffin-embedded tissue sample very thinly with a microtome. Prior to embedding the tissue sample, the tissue sample is pretreated in various solutions appropriate to the examination. Typically, prior to paraffin embedding, the tissue sample is fixed, dehydrated, cleared, infiltrated with molten paraffin and, depending on the test, stained. Such prior treatment of the tissue samples requires subjecting the tissue sample to contact with various fluids, including ethanol, xylene, formaldehyde and water.
The trend in histological examination is to take much smaller samples through less invasive techniques. This creates several problems for the histology laboratory. One problem is that currently available processing cassettes have apertures large enough to permit the tissue sample to escape from the cassette during processing. A further problem is that presently available cassettes have right angle walls. During the final treatment of the tissue sample in the cassette, the sample is immersed in molten wax. As the wax begins to harden, the sample is removed from the cassette and placed into the bottom portion of an embedding mold. However, the right angle walls of the present cassettes result in creating a capillary action along the wall which tends to move the sample up the wall. Because of the small size of the sample, the sample can be very difficult to locate in the cassette for removal to the embedding mold.
U.S. Pat. No. 5,080,869 to McCormick is directed to a typical prior art cassette. As shown in FIG. 1 of the McCormick patent, the wall apertures and the bottom apertures are elongated slots having a relatively wide width. The cassette walls are at right angles to the bottom wall.
U.S. Pat. No. 5,269,671 to McCormick also discloses a cassette with slot like apertures and right angle side walls.
Accordingly, it is a principal object of the present invention to provide a cassette for use in the treatment of small tissue specimens for histological examination.
This and other objects of the invention will become more apparent from the following detailed description and the accompanying drawings.